(a) Field of the Invention
The present invention relates generally to a hot air torch and in particular to a nozzle assembly for a hot air torch.
(b) Background Art
Hot air torches which have a handle portion and a nozzle portion are already known in the prior art. At the handle portion, a first pipe carries pressurized air, and a second pipe carries propane gas under pressure. The first pipe carrying pressurized air leads into a block which splits the air into first and second air passageways. The passageways each have a valve by which flow can be regulated. The propane that travels through the second pipe passes through a conduit, and it is directed to a fuel exhaust outlet defined by a fuel discharge nozzle. The pressurized air from the first passageway travels into another passageway portion, and then into an annular plenum which surrounds an inner burner tube or housing. The burner tube has at its rear end circumferentially spaced radially inwardly directed air jet openings. The compressed air from the plenum goes through the jet openings and travels radially inwardly toward the nozzle outlet. This air then travels with the propane forward through the burner tube or housing and the air mixes with the propane. The mixture of propane and compressed air ignite within the burner tube and within a main cylindrical outer housing, and the flame travels outwardly through the main housing and also heats the air in the second air passageway. Hot exhaust gases proceed from the front opening of the main housing and compressed air flows through the exhaust outlet nozzle for the second air passageway.
In the prior art torch described above, there was provided a discharge nozzle of conventional design, where the lateral surfaces of the discharge nozzle were longitudinally aligned in the pattern of a regular hexagon. While the hot air torch generally served its primary function of supplying heat from the combustion products in the main housing, and also heating the high velocity air traveling through the second passageway, it was felt that there was need for improvement. This led to the development of the present invention which is an improved nozzle assembly for such a hot air torch.
A search of the U.S. patent literature has disclosed a number of prior art patents, these being the following:
U.S. Pat. No. 4,462,794 to Vosper et al. discloses a method of operating a wall-fired duct heater and a burner in which the various air paths enter radially to the axis of the fuel feed.
U.S. Pat. No. 4,416,613 to Barisoff discloses a blow pipe type of burner in which there is an axially extending burner tube connected to a mixing chamber. There are radial air inlet openings that allow air to enter a fuel air mixing chamber and air for cooling is supplied to a space in front of the burner. The improvement of Barisoff is a self cooling shield.
U.S. Pat. No. 4,082,497 to Crawford et al. teaches a high capacity quiet burner for a hot air heating system which has an open outlet end and a closed inlet end, and a secondary air flow over the burner area is provided to a space where the secondary air and the flame exhaust mix. This provides a quiet combustion process in which it is alleged that there is uniform and stable combustion.
U.S. Pat. No. 3,851,050 to Groenendaal et al. discloses a sulphur dioxide burner with a radial oxygen feed.
U.S. Pat. No. 3,156,452 to Flynn teaches a heater with a radial air feed wherein air enters behind rather than in front of the fuel nozzle.
U.S. Pat. No. 2,107,365 to Bray discloses a burner in which air enters the burner chamber and by radial openings and additional air to be heated enters a second chamber through the radial openings.
U.S. Pat. No. 1,172,755 to Wilson shows an oil burner in which air is fed radially both behind the fuel feed, and in the combustion chamber.
U.S. Pat. No. 316,059 to Randol shows a burner with a combustion chamber having air openings.
U.S. Pat. No. Re. 28,665 to Zagoroff discloses a heat gun with air at both the flame area and the secondary mixing area that is radially fed.